Display screen or a portion thereof with a graphical user interface



The FIGURE is a front view of an image of a graphical user interface for a display screen or a portion thereof.

The outermost broken lines in the FIGURE showing a display screen or portion thereof illustrate portions of the article, and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or a portion thereof with a graphical user interface, as shown and described. 